Macro-meso pullout behavior of three-dimensional geogrids with different transverse rib spacings

Geogrid serve as crucial reinforcement materials, with pullout behavior playing a key role in ensuring infrastructure stability. To investigate the pull-out behavior of the geogrid-soil interface in three-dimensional geogrids, specimens with varying geometric specifications were fabricated using 3D printing technology. Laboratory-scale pull-out tests combined with discrete element method (DEM) simulations were conducted to analyze the macroscopic and mesoscopic responses of three-dimensional geogrids with varying transverse rib spacings. The results indicate that reductions in transverse rib spacing were associated with increases in both peak pull-out force and peak strain of three-dimensional geogrids. Higher stiffness was observed for geogrids with smaller transverse rib spacing, which more effectively enhanced the tensile capacity of the structural surface. Furthermore, significant increases in peak shear stress at the geogrid-soil interface were observed with decreasing transverse rib spacing. Interface cohesion increased by 30.59%-37.15%. A 3.21% increase in the average coordination number of sand particles was also observed for geogrids with smaller transverse rib spacing, accompanied by a denser and more interconnected force-chain network, resulting in compact and uniform stress transmission paths. With increasing pull-out displacement, continuous shear bands were observed to develop at soil-reinforcement interface, and geogrids with smaller rib spacing exhibited a stronger tendency for shear band formation. Overlapping influence zones between adjacent transverse ribs in denser-spacing geogrids facilitated continuous interlocking behavior, enhancing overall interlocking effect.